TWRP Nandroid restore - kernel ?!

When restoring a Nandroid backup in TWRP, selecting only the "system" and "data" partitions, does it not also restore the previous kernel ?!
In others words, isn't the kernel stored in the "system" partition?

I just restored one, "system" and "data", and was surprised to find that the kernel I flashed after I took the backup is still present...

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